Base station, method for radio communication, radio communication system, and radio terminal

ABSTRACT

Provided is a base station including a transmitter section that transmits a radio signal in a frame including a control region and a data region, a control signal generating section that generates a control signal which includes reference information identified by a group identifier assigned to a plurality of radio terminals and which is transmitted in the control region, and a data signal generating section that generates a data signal by disposing information for the plurality of radio terminals in a reference region indicated by the reference information in the data region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 15/706,932, filed Sep. 18, 2017 which is acontinuation application of U.S. patent application Ser. No. 13/816,946,filed Feb. 14, 2013, which is a national stage entry of PCT applicationPCT/JP2011/068367 filed Aug. 11, 2011 and which claims the benefit ofJapanese Priority Patent Application 2010-225080 filed Oct. 4, 2010, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a base station, a method for radiocommunication, a program, a radio communication system, and a radioterminal.

BACKGROUND ART

Currently, standardization of a 4G radio communication system is underprogress by 3GPP (Third Generation Partnership Project). According tothe 4G, an improvement in maximum communication speed and a qualityimprovement in cell edges can be realized by using technologies such asrelays and carrier aggregation. Further, considerations are given toimproving coverage by introducing base stations other than eNodeB(macro-cell base station), such as HeNodeB (Home eNodeB, femtocell basestation, compact base station for cell phones) and RHH (Remote RadioHead).

(Blind Decoding)

In a radio communication system as above, the base station notifies anassignment of a receiver resource to a UE (Downlink Assign), a grant ofa transmitter resource (Uplink Grant) and the like by a control signalcalled PDCCH (Phy Downlink Control Channel). Here, resource informationsuch as the Downlink Assign and the Uplink Grant are information foreach UE (User Equipment). Due to this, the base station transmits thecontrol signal so that each UE can extract the resource informationaddressed to itself, and each UE extracts the resource informationaddressed to itself from the PDCCH by a process called blind decoding.Hereinbelow, this feature will be described in detail.

The base station describes resource information addressed to each UE insmallest units of the control signal called CCE (Control ChannelElement). Further, the base station adds, to the CCE, check bits thatare obtained by CRC (Cyclic Redundancy Check) by masking the resourceinformation with C-RNTI (Cell Radio Network Temporary Identify) that isan identifier unique to each UE.

When the PDCCH including a plurality of the aforementioned CCEs isreceived, the UE performs the CRC check by demasking each CCE by theUE's own C-RNTI. That is, the UE performs the CRC check of each CCE onan assumption that each CCE is addressed to itself, and determines theCCE with a normal result as the CCE addressed to itself. The aboveprocess by the UE is called the blind decoding, and such a blinddecoding is described for example in Patent Literature 1.

(MTC)

On the other hand, debates on MTC (Machine Type Communications) are alsoin progress in the 3GPP. The MTC is generally synonymous to M2M (Machineto Machine), and refers to a communication between machines and notdirectly used by a human. The MTC primarily is performed between aserver and a MTC terminal that is not directly used by a human.

For example, as a medical application of the MTC, a case may be assumedin which an MTC terminal collects electrocardiogram information of ahuman, and transmits the electrocardiogram information to a server byusing uplink when a certain trigger condition is met. As anotherapplication of the MTC, a case may be assumed in which a vending machineis caused to function as an MTC terminal, and a server causes thevending machine under management to report sales once every certaincycle (for example, every 30 days).

Such an MTC terminal by way of example has the following features ingeneral, however, not every MTC terminal needs to have all of thefollowing features, and which of the features is to be endowed dependson applications.

Scarce needs to move (Low Mobility)

Transmission of small data (Online Small Data Transmission)

Very low power consumption (Extra Low Power Consumption)

Handled by grouping respective MTCs (Group-based MTC Features)

CITATION LIST Patent Literature

Patent Literature 1:

JP 2009-296589A

SUMMARY OF INVENTION Technical Problem

However, due to the introduction of the aforementioned MTCs, increasesare expected in a number of terminals existing within each cell, anumber of terminals a base station is to contain in an Active mode, anda number of terminals for the base station to simultaneously control inthe PDCCH. Further, the CCE included in the PDCCH also increasesaccompanying the increase in the number of terminals simultaneouslycontrolled in the PDCCH.

As a result, load of the blind decoding in the UE increases due to arange requiring the blind decoding by the UE (including the MTCterminal) being broader. Especially, there are cases in which theextra-low power consumption is required in the MTC terminal, so theincrease in the load of the blind decoding is problematic.

The invention has been created in view of the above problem, and an aimof the invention is to provide a novel and improved base station, methodfor radio communication, program, radio communication system, and radioterminal capable of suppressing the load of the blind decoding in theradio terminal.

Solution to Problem

According to an embodiment of the present disclosure, there is provideda base station including a transmitter section that transmits a radiosignal in a frame including a control region and a data region, acontrol signal generating section that generates a control signal whichincludes reference information identified by a group identifier assignedto a plurality of radio terminals and which is transmitted in thecontrol region, and a data signal generating section that generates adata signal by disposing information for the plurality of radioterminals in a reference region indicated by the reference informationin the data region.

The data signal generating section may dispose information for each ofthe plurality of radio terminals in the reference region indicated bythe reference information, the information being identified by aterminal identifier of each of the plurality of radio terminals.

The information for each of the plurality of radio terminals may includeuplink resource information or downlink resource information.

The uplink resource information or the downlink resource information mayindicate a resource in a frame that is provided after a frame in whichthe information for each of the plurality of radio terminals isdisposed.

The data signal generating section may dispose the information for theplurality of radio terminals in a same reference region within the dataregion over a plurality of frames, the same reference region beingindicated by the reference information disposed in a control region ofone frame.

An uplink group identifier and a downlink group identifier may beassigned to the plurality of radio terminals, the data signal generatingsection may dispose uplink resource information for each of theplurality of radio terminals in a reference region indicated byreference information identified by the uplink group identifier, and thedata signal generating section may dispose downlink resource informationfor each of the plurality of radio terminals in a reference regionindicated by reference information identified by the downlink groupidentifier.

The control signal generating section may dispose reference informationidentified by a same group identifier in a predetermined frequencyregion within the control region.

The control signal generating section may add a check bit obtained bymasking the reference information with the group identifier to thereference information.

According to another embodiment of the present disclosure, there isprovided a method for radio communication, the method including thesteps of generating a control signal that is to be transmitted in acontrol region in a frame including the control region and a dataregion, the control signal including reference information identified bya group identifier assigned to a plurality of radio terminals,generating a data signal by disposing information for the plurality ofradio terminals in a reference region indicated by the referenceinformation in the data region, and transmitting the control signal andthe data signal.

According to another embodiment of the present disclosure, there isprovided a program for causing a computer to function as a transmittersection that transmits a radio signal in a frame including a controlregion and a data region, a control signal generating section thatgenerates a control signal which includes reference informationidentified by a group identifier assigned to a plurality of radioterminals and which is transmitted in the control region, and a datasignal generating section that generates a data signal by disposinginformation for the plurality of radio terminals in a reference regionindicated by the reference information in the data region.

According to another embodiment of the present disclosure, there isprovided a radio communication system including a plurality of radioterminals, and a base station that includes a transmitter section thattransmits a radio signal in a frame including a control region and adata region, a control signal generating section that generates acontrol signal which includes reference information identified by agroup identifier assigned to the plurality of radio terminals and whichis transmitted in the control region, and a data signal generatingsection that generates a data signal by disposing information for theplurality of radio terminals in a reference region indicated by thereference information in the data region.

According to another embodiment of the present disclosure, there isprovided a radio terminal including a receiver section that receives aradio signal transmitted from a base station in a frame including acontrol region and a data region, and an acquiring section that acquiresreference information identified by a group identifier assigned to aplurality of radio terminals including the radio terminal from a controlsignal received in the control region, and a data portion identified bya terminal identifier assigned to the radio terminal from a data signalreceived in a reference region indicated by the reference information inthe data region.

The acquiring section may acquire the data portion identified by theterminal identifier assigned to the radio terminal from the controlsignal received in the control region in a case of determining that thegroup identifier is not used by the base station.

According to another embodiment of the present disclosure, there isprovided a method for radio communication performed by a radio terminal,the method including the steps of receiving a radio signal transmittedfrom a base station in a frame including a control region and a dataregion, acquiring reference information identified by a group identifierassigned to a plurality of radio terminals including the radio terminalfrom a control signal received in the control region, and acquiring adata portion identified by a terminal identifier assigned to the radioterminal from a data signal received in a reference region indicated bythe reference information in the data region.

According to another embodiment of the present disclosure, there isprovided a program for causing a computer to function as a radioterminal that includes a receiver section that receives a radio signaltransmitted from a base station in a frame including a control regionand a data region, and an acquiring section that acquires referenceinformation identified by a group identifier assigned to a plurality ofradio terminals including the radio terminal from a control signalreceived in the control region, and a data portion identified by aterminal identifier assigned to the radio terminal from a data signalreceived in a reference region indicated by the reference information inthe data region.

Advantageous Effects of Invention

According to the invention as described above, the load of the blinddecoding in the radio terminal can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram showing an example of a configurationof a radio communication system.

FIG. 2 is an explanatory diagram showing a 4G frame format.

FIG. 3A is an explanatory diagram showing an example of using one Ofdmsymbol in a transmission of a PDCCH.

FIG. 3B is an explanatory diagram showing an example of using two Ofdmsymbols in the transmission of the PDCCH.

FIG. 3C is an explanatory diagram showing an example of using three Ofdmsymbols in the transmission of the PDCCH.

FIG. 4 is an explanatory diagram showing a resource block.

FIG. 5 is an explanatory diagram showing a specific example of a CCE.

FIG. 6 is an explanatory diagram showing blind decoding.

FIG. 7 is an explanatory diagram showing the blind decoding.

FIG. 8 is a sequence diagram showing an example of a method of assigningC-RNTI and MTC-GP_RNTI.

FIG. 9 is an explanatory diagram showing a configuration of a basestation of a first embodiment of the invention.

FIG. 10 is an explanatory diagram showing a dispositional relationshipof a CCE, a second search space, and an allotted resource.

FIG. 11 is an explanatory diagram showing a configuration of an MTCterminal of the first embodiment.

FIG. 12 is a sequence diagram showing an operation of the radiocommunication system of the first embodiment of the invention.

FIG. 13 is a sequence diagram showing an example of a method of changingan RNTI used for the blind decoding.

FIG. 14 is an explanatory diagram showing an example of disposition ofthe second search space for a certain MTC group.

FIG. 15 is an explanatory diagram showing an example of disposition ofthe CCE for each MTC group.

FIG. 16 is an explanatory diagram showing a specific example of an MTCgroup to which MTC terminals belong.

FIG. 17 is an explanatory diagram corresponding to a fourth embodiment.

FIG. 18 is an explanatory diagram showing a relationship of a referenceresource block and an uplink resource block of each MTC terminal.

FIG. 19 is an explanatory diagram showing a modification of therelationship of the reference resource block and the uplink resourceblock of each MTC terminal.

FIG. 20 is an explanatory diagram showing an operation of a radiocommunication system of a fifth embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the drawings, elements that have substantiallythe same function and structure are denoted with the same referencesigns, and repeated explanation is omitted.

Further, in the description and the drawings, there may also be cases inwhich a plurality of constituent features having substantially the samefunctional configuration is distinguished by adding different alphabetsafter the same reference sign. For example, the plurality of constituentfeatures having substantially the same functional configuration may bedistinguished as MTC terminals 20A, 20B, and 20C. However, in caseswhere the respective one of the plurality of constituent features havingsubstantially the same functional configuration does not need to beparticularly distinguished, only the same reference sign will be given.For example, when the MTC terminals 20A, 20B, and 20C do notparticularly need to be distinguished, each will simply be termed a MTCterminal 20.

Further, the “mode to carry out the invention” will be described inaccordance with the order in the below appendix.

1. Overview of Radio Communication System

1-1. Overview of radio communication system

1-2. Configuration of frame

1-3. Configuration of PDCCH

1-4. Blind decoding

2. Description of Respective Embodiments

2-1. First embodiment

(Base station of first embodiment)

(MTC terminal of first embodiment)

(Operation of first embodiment)

(Supplementation of first embodiment)

2-2. Second embodiment

2-3. Third embodiment

2-4. Fourth embodiment

2-5. Fifth embodiment

2-6. Sixth embodiment

2-7. Seventh embodiment

3. Conclusion

1. OVERVIEW OF RADIO COMMUNICATION SYSTEM

Currently, standardization of a 4G radio communication system is inprogress in 3GPP. Embodiments of the invention can be adapted to the 4Gradio communication system by way of examples, so an overview of the 4Gradio communication system will be described.

[1-1. Configuration of Radio Communication System]

FIG. 1 is an Explanatory Diagram Showing an Example of a Configurationof a Radio communication system 1. As shown in FIG. 1, the radiocommunication system 1 includes a base station 10, a core networkincluding an MME (Mobility Management Entity) 12, an S-GW (ServingGateway) 14, and a PDN (Packet Data Network)-GW 16, MTC terminals 20,and an MTC server 30.

Embodiments of the invention can be adapted to radio communicationdevices such as the base station 10 and the MTC terminals 20 shown inFIG. 1. Notably, the base station 10 may for example be an eNodeB, arelay node, or a Home eNodeB that is a compact base station for homeuse. Further, the MTC terminals 20 are examples of user equipment (UE),and adaptations to non-MTC terminals such as a cell phone, PC (PersonalComputer), and the like is also possible as embodiments of theinvention.

The base station 10 is a radio base station that communicates with theMTC terminals 20. Although only one base station 10 is shown in FIG. 1,a large number of base stations 10 are connected to the core network inreality. Further, although depiction in FIG. 1 is omitted, the basestation 10 communicates also with other user equipments such as anon-MTC terminal.

The MME 12 is a device that performs controls of settings, opening, andhand-over of a data communication session. The MME 12 is connected tothe base station 10 via an interface called X2.

The S-GW 14 is a device that performs routing and transfer of user data.The PDN-GW 16 functions as a connecting node with an IP service network,and transfers the user data to and from the IP service network.

The MTC terminals 20 are radio terminals specialized for MTC, which is acommunication between machines and is not used directly by a human,which is under discussion in the 3GPP. The MTC terminals 20 performradio communication in accordance with an application with the basestation 10. Further, the MTC terminals 20 perform bidirectionalcommunication with the MTC server 30 via the core network.

For example, as a medical application of the MTC, a case may be assumedin which an MTC terminal 20 collects electrocardiogram information of ahuman, and transmits the electrocardiogram information to the server byusing uplink when a certain trigger condition is met. As anotherapplication of the MTC, a case may be assumed in which a vending machineis caused to function as the MTC terminal 20, and the MTC server 30causes the vending machine under management to report sales once everycertain cycle (for example, every 30 days).

Such an MTC terminal 20 by way of example has the following features ingeneral, however, not every MTC terminal 20 needs to have all of thefollowing features, and which of the features is to be assigned dependson applications.

Scarce needs to move (Low Mobility)

Transmission of small data (Online Small Data Transmission)

Very low power consumption (Extra Low Power Consumption)

Handled by grouping respective MTCs (Group-based MTC Features)

[1-2. Configuration of Frame]

Although details of the aforementioned base station 10 and MTC terminals20 are not decided, they are expected to perform radio communicationconforming to communication between the eNodeB and the UE. Thus,hereinbelow, a radio frame shared between the eNodeB and the UE will bedescribed. Contents to be described hereinbelow can be applied to thecommunication between the base station 10 and the MTC terminals 20.

FIG. 2 is an explanatory diagram showing a 4G frame format. As shown inFIG. 2, a 10 ms radio frame is configured of ten 1 ms sub frames #0 to#9. Further, each 1 ms sub frame is configured of two 0.5 ms slots.Further, each 0.5 ms slot is configured of seven Ofdm symbols.

Notably, the Ofdm symbol is a unit used in a communication scheme of anOFDM (Orthogonal Frequency Division Multiplexing) modulation system, andis a unit by which data processed in one FFT (Fast Fourier Transform) isoutputted.

At a head of each 1 ms sub frame shown in FIG. 2, a control signalcalled a PDCCH (Phy Downlink Control Channel) is added. As shown inFIGS. 3A, 3B, and 3C, one Ofdm symbol to three Ofdm symbols at the headof the sub frame are used for a transmission of the PDCCH. That is,there are cases in which one Ofdm symbol is used for the PDCCHtransmission, and there also are cases in which three Ofdm symbols areused for the PDCCH transmission.

Notably, a region in the radio frame used for the PDCCH transmission iscalled a control region, and a region in the radio frame used fortransmissions of a PDSCH (Phy Downlink Shared Channel) or a PUSCH (PhyUplink Shared Channel) is called a data region.

[1-3. Configuration of PDCCH]

Next, control information included in the PDCCH will be described.Although various types of control information are included in the PDCCH,the following two pieces of control information are primarily included.

(1) Assigning information indicating a resource block that the UE is toreceive from among the PDSCH (assign)

(2) Granting information indicating a resource block that the UE is totransmit from among the PUSCH (grant)

Notably, as shown in FIG. 4, a minimum unit of the resource block istwelve subcarriers×seven Ofdm symbols. Further, other than the resourceinformation for example of assign, grant, and the like, the PDCCHfurther includes power control information, paging indexes, systeminformation and the like.

[1-4. Blind Decoding]

The resource information such as assign and grant as above areinformation for each UE. Due to this, the eNodeB transmits the PDCCH sothat each UE can extract the resource information addressed to itself,and each UE extracts the resource information addressed to itself fromthe PDCCH by a process called blind decoding. Hereinbelow, this featurewill be described in detail.

In the PDCCH, the minimum unit of the control information for each UE iscalled CCE (Control Channel Element). The eNodeB includes the resourceinformation for each UE, and generates CCEs identified by a C-RNTI (CellRadio Network Temporary Identify) that is an identifier of each UE.Hereinbelow, specific examples of the CCE will be described withreference to FIG. 5.

FIG. 5 is an explanatory diagram showing a specific example of the CCE.As shown in FIG. 5, the CCE includes target information such as theresource information, as well as a check bit that is obtained by a CRC(Cyclic Redundancy Check) by masking the resource information with theC-RNTI (Cell Radio Network Temporary Identify). Here, the masking may bean exclusive disjunction calculation (XOR) of the resource informationand the C-RNTI, or may be a serial coupling of the resource informationand the C-RNTI.

When the PDCCH including the aforementioned plurality of CCEs isreceived, the UE extracts the CCE identified by its own C-RNTI by theblind decoding. Hereinbelow, a more specific description will be givenwith reference to FIG. 6 and FIG. 7.

FIG. 6 and FIG. 7 are explanatory diagrams showing the blind decoding.As shown in FIG. 6, as the blind decoding, the UE performs CRC check bydemasking each CCE with its own C-RNTI. Further, the UE performs theblind decoding on each CCE in an order shown in FIG. 7. That is, the UEperforms the CRC check of each CCE on an assumption that each CCE isaddressed to itself, and determines the CCE with a normal result as theCCE addressed to itself.

(Cce Aggregation)

Notably, in connection to the aforementioned CCEs, there is a conceptcalled CCE aggregation. The CCE aggregation is a mode in which CCEs aretransmitted at an amount that is one, two, four, or eight times thetypical unit of the CCE.

For example, in a cell with a large cell radius, when an SN (signal tonoise ratio) of a UE can be predicted to be small, the CCEs aretransmitted by being repeated eight times. In this case, the check bitby the CRC is added to the result of the eight times of repetition.Accordingly, the UE performs the blind decoding by taking into account apossibility that the CCE aggregation has been performed.

Further, other than the C-RNTI, RNTIs such as a P-RNTI for acquiringinformation for paging and an SI-RNTI for acquiring system informationexist. Accordingly, the UE performs the blind decoding by assuming bywhich of the RNTIs each of the CCEs is to be identified.

(Particulars of Achieving the Embodiments of the Invention)

Incidentally, in the 4G radio communication system, due to theintroduction of the aforementioned MTC terminals, increases are expectedin a number of terminals existing within each cell, a number ofterminals the base station is to contain in an Active mode, and a numberof terminals for the base station 10 to simultaneously control in thePDCCH. Further, the CCE included in the PDCCH also increasesaccompanying the increase in the number of terminals simultaneouslycontrolled in the PDCCH.

As a result, load of the blind decoding in the UE increases due to arange requiring the blind decoding by the UE (including the MTCterminal) being broader. Especially, there are cases in which theextra-low power consumption is required in the MTC terminal, so theincrease in the load of the blind decoding is problematic.

Thus, the embodiments of the invention have been created with the abovecircumstance as a point of concern. According to the embodiments of theinvention, load of the blind decoding in the MTC terminal 20 can besuppressed. Hereinbelow, such embodiments of the invention will bedescribed in detail.

2. DESCRIPTION OF RESPECTIVE EMBODIMENTS

As described in detail in “2-1. First embodiment” to “2-7. Seventhembodiment” by way of example, the invention can be implemented invarious manners. Further, each embodiment is implemented by using anMTC-GP_RNTI which is an identifier of an MTC group assigned to the MTCterminal 20. Thus, prior to the detailed description of the respectiveembodiments, a method of assigning the MTC-GP_RNTI to each MTC terminal20 will be described.

(Assigning MTC-GP_RNTI)

FIG. 8 is a sequence diagram showing an example of a method of assigningC-RNTI and MTC-GP_RNTI. As shown in FIG. 8, firstly, in a random accessprocedure formed of Step 1 to Step 4, the C-RNTIs are assigned to eachMTC terminal 20.

More specifically described, the MTC terminal 20 transmits a preamble toa random access window in a radio frame (Step 1). In successfullyreceiving the preamble from the MTC terminal 20, the base station 10transmits a random access response to the MTC terminal 20 (Step 2). Thebase station 10 assigns a Temporary C-RNTI to the MTC terminal 20 inthis random access response.

Then, when the random access response is received, the MTC terminal 20transmits an L2/L3 message to the base station 10 (Step 3). Inconnection to the above, the MTC terminal 20 determines that a randomaccess had been successful by receiving a contention resolution messagetransmitted from the base station 10 (Step 4), and begins using theTemporary C-RNTI assigned in Step 2 as the C-RNTI.

Thereafter, an MTC category setting procedure formed of Step 5 and Step6 is performed. More specifically described, since the MTC terminal 20is set with information of an MTC category indicating whether the MTCterminal 20 itself is an MTC terminal or not, the MTC terminal 20 isaware that itself is an MTC terminal. Due to this, the MTC terminal 20notifies the base station 10 of the MTC category (Step 5), and receivesa notification confirming signal from the base station 10 (Step 6).Notably, the MTC category may include information indicating a capacityof the MTC terminal 20, such as whether the MTC terminal 20 is compliantwith a long sleep mode for over one month or not.

Further, in an MTC-GP_RNTI setting procedure formed of Step 7 and Step8, the MTC-GP_RNTI is assigned to the MTC terminal 20. More specificallydescribed, the MTC terminal 20 performs an MTC group setting request tothe base station 10 (Step 7). The base station 10 transfers theaforementioned setting request to the MME 12 together with a terminal IDof the MTC terminal 20 (a unique number described in an SIM, and isdifferent from the RNTI).

The MME 12 is a device that handles the unique information of theterminals, receives correspondence information of an MTC group and theterminal IDs of the terminals that are granted to enter the MTC groupfrom the MTC server 30, and retains the correspondence information. TheMME 12 determines whether an MTC terminal 20 having the terminal IDtransferred from the base station 10 is allowed to enter the MTC groupor not based on the correspondence information, and if the MTC terminal20 is allowed to enter, the MME 12 transmits an MTC group settingconfirming signal to the base station 10.

Subsequently, the base station 10 transmits the MTC-GP_RNTI to the MTCterminal 20 together with the MTC group setting confirming signal (Step8). Then, the MTC terminal 20 becomes capable of using the MTC-GP_RNTIby receiving the MTC group setting confirming signal and the MTC-GP_RNTIfrom the base station 10.

The method of assigning the MTC-GP_RNTI is described above, however, themethod of assigning the MTC-GP_RNTI is not limited to the above example.For example, information such as an AC (Access Class) that ispredeterminedly set in the MTC terminal 20 may be used as theMTC-GP_RNTI, and the MTC-GP_RNTI may be assigned to the MTC terminal 20by a human operation.

2-1. First Embodiment

Next, the first embodiment of the invention will be described withreference to FIG. 9 to FIG. 13.

(Base Station of First Embodiment)

FIG. 9 is an explanatory diagram showing a configuration of a basestation 10 of the first embodiment of the invention. As shown in FIG. 9,the base station 10 of the first embodiment includes an antenna 104, aradio processing section 108, a storage section 112, a scheduler 116, acontrol signal generating section 120, a CRC circuit 124, and a datamapping section 128.

The antenna 104 functions as a transmitter section that transmits atransmitter signal such as a PDCCH (control signal) and a PDSCH (datasignal) supplied from the radio processing section 108 as a radiosignal, and as a receiver section that converts the radio signaltransmitted from a radio communication device such as an MTC terminal 20into an electric receiver signal, and supplies the receiver signal tothe radio processing section 108. Notably, in FIG. 9, although anexample in which the base station 10 includes one antenna is shown, thebase station 10 may include a plurality of antennas. In this case, thebase station 10 is capable of realizing an MIMO (Multiple Input,Multiple Output) communication, a diversity communication and the like.

The radio processing section 108 performs radio processes fortransmission such as modulation, DA conversion, filtering,amplification, and up-conversion of the transmitter signal such as thePDCCH supplied from the control signal generating section 120, the PDSCHsupplied from the data mapping section, and the like. Further, the radioprocessing section 108 performs radio processes for reception such asdown-conversion, filtering, DA conversion, and demodulation of thereceiver signal supplied from the antenna 104.

The storage section 112 stores the MTC-GP_RNTIs, the C-RNTIs and thelike that are assigned to the respective MTC terminals 20. Further,although depiction is omitted in FIG. 9, the storage section 112 alsostores other RNTIs such as SI-RNTIs, P-RNTIs, and RA-RNTIs.

The scheduler 116 allots a resource to each MTC terminal 20 for datacommunication. That is, the scheduler 116 allots resource blocks amongthe PDSCH that the respective MTC terminals 20 are to receive, andresource blocks among the PUSCH that the respective MTC terminals 20 areto transmit.

The control signal generating section 120 generates a PDCCH formed of aplurality of CCEs. To describe in further detail, the control signalgenerating section 120 generates a CCE including information indicatinga second search space arranged within data region (referenceinformation) and a check bit obtained by the CRC circuit 124 by maskingthe aforesaid information by the MTC-GP_RNTI. Here, the masking may bean exclusive disjunction calculation (XOR) of the information indicatingthe second search space and the MTC-GP_RNTI, or may be a serial couplingof the information indicating the second search space and the C-RNTI.According to the above configuration, an MTC terminal 20 within an MTCgroup to which the MTC-GP_RNTI is assigned can be designated as adestination of the information indicating the second search space.

Notably, although an example in which the check bit corresponding to theinformation indicating the second search space is added to designate thedestination of the CCE is described above, a method of designating thedestination of the CCE is not limited to the above example. For example,the control signal generating section 120 may designate the designationof the CCE simply by attaching the MTC-GP_RNTI to the informationindicating the second search space.

Further, the control signal generating section 120 generates informationfor mapping in the second search space, and supplies the same to thedata mapping section 128 together with information indicating a positionof the second search space. Here, the information for mapping in thesecond search space is the resource information for the respective MTCterminals 20 within the MTC group to which the MTC-GP_RNTI is assigned.Further, a check bit obtained by the CRC circuit 124 by masking theaforesaid information with the C-RNTIs of the respective MTC terminals20 is added to the resource information for the respective MTC terminals20.

The data mapping section 128 (data signal generating section) maps userdata for each MTC terminal 20 supplied from an upper layer in theresource block allotted by the scheduler 116 among the PDSCH that therespective MTC terminals 20 are to receive. Further, the data mappingsection 128 maps the resource information of the respective MTCterminals 20 supplied from the control signal generating section 120 inthe second search space. Hereinbelow, a disposition relationship of theCCE, the second search space, the allotted resource and the like will bedescribed more specifically with reference to FIG. 10.

FIG. 10 is an explanatory diagram showing the disposition relationshipof the CCE, the second search space, and the allotted resource. In theexample shown in FIG. 10, a CCE #1 describes information indicating aposition of a second search space #1 for an MTC group having anMTC-GP_RNTI corresponding to a check bit added to the CCE #1.

Then, among a plurality of resource information included in the secondsearch space #1, for example, resource information #1 indicates aresource block #1 for the MTC terminal 20 having a C-RNTI correspondingto a check bit added to the resource information #1. Further, theresource information #2 indicates a resource block #2 for the MTCterminal 20 having a C-RNTI corresponding to a check bit added to theresource information #2.

Similarly, a CCE #2 shown in FIG. 10 describes information indicating aposition of a second search space #2 for an MTC group having anMTC-GP_RNTI corresponding to a check bit added to the CCE #2. Further,of a plurality of resource information included in the second searchspace #2, for example, resource information #3 indicates a resourceblock #3 for the MTC terminal 20 having a C-RNTI corresponding to acheck bit added to the resource information #3.

Notably, the CCE and the second search space may be disposed in the samesub frame as with the CCE #1 and the second search space #1, or may bedisposed in different sub frames as with the CCE #2 and the secondsearch space #2. Such a relationship of the CCE and the second searchspace may fixedly be set by signaling in advance, or may be designatedby the CCE.

Further, since processing cannot be performed timely if the resourceblocks indicated by the respective resource information included in thesecond search space are in the same sub frame as the second searchspace, the resource blocks are disposed in a sub frame that is after thesub frame of the second search space, such as with the resource block #1and the resource block #2. Such a relationship of the second searchspace and the allotted resource blocks of the respective MTC terminals20 may fixedly be set by signaling in advance, or may be designated bythe second search space.

(MTC Terminal of First Embodiment)

Hereabove, the configuration of the base station 10 of the firstembodiment of the invention was described. Now, a configuration of theMTC terminal 20 of the first embodiment of the invention will bedescribed.

FIG. 11 is an explanatory diagram showing the configuration of the MTCterminal 20 of the first embodiment. As shown in FIG. 11, the MTCterminal 20 of the first embodiment includes an antenna 204, a radioprocessing section 208, a storage section 212, a blind decoding section220, and a CRC circuit 224.

The antenna 204 functions as a transmitter section that transmits atransmitter signal such as a PUSCH(data signal) supplied from the radioprocessing section 208 as a radio signal, and as a receiver section thatconverts the radio signal such as the PDCCH and the PDSCH transmittedfrom a base station 10 into an electric receiver signal, and suppliesthe receiver signal to the radio processing section 208. Notably, inFIG. 11, although an example in which the MTC terminal 20 includes oneantenna is shown, the MTC terminal 20 may include a plurality ofantennas. In this case, the MTC terminal 20 is capable of realizing anMIMO (Multiple Input, Multiple Output) communication, a diversitycommunication and the like.

The radio processing section 208 performs radio processes fortransmission such as modulation, DA conversion, filtering,amplification, and up-conversion of user data supplied from an upperlayer. Further, the radio processing section 208 performs radioprocesses for reception such as down-conversion, filtering, DAconversion, and demodulation of the receiver signal supplied from theantenna 104.

The storage section 212 stores for example the MTC-GP_RNTIs, the C-RNTIsand the like that are assigned from the base station 10. Further,although depiction is omitted in FIG. 11, the storage section 212 alsostores other RNTIs such as SI-RNTI, P-RNTI, and RA-RNTI.

When the PDCCH is supplied from the radio processing section 208, theblind decoding section 220 (acquiring section) extracts the CCEidentified by the MTC-GP_RNTI assigned to the MTC terminal 20 by theblind decoding. More specifically described, the blind decoding section220 operates in cooperation with the CRC circuit 224 to perform CRCcheck by demasking each CCE by the MTC-GP_RNTI assigned to the MTCterminal 20. Then, the blind decoding section 220 extracts the CCE witha normal result, and specifies the second search space based on theinformation described in the CCE. For example, the blind decodingsection 220 extracts the CCE #1 shown in FIG. 10 from the PDCCH, andspecifies the second search space #1 based on the information describedin the CCE #1.

Further, when the PDSCH is supplied from the radio processing section208, the blind decoding section 220 acquires the resource informationaddressed to itself by performing the blind decoding using the C-RNTI onthe second search space specified from the CCE. More specifically, theblind decoding section 220 operates in cooperation with the CRC circuit224 to perform CRC check by demasking each resource information in thesecond search space using the C-RNTI. Then, the blind decoding section220 acquires the resource information with a normal result as theresource information addressed to itself. Thereafter, the radioprocessing section 208 performs the transmission process or thereception process in the resource block indicated by the resourceinformation. For example, the blind decoding section 220 acquires theresource information #1 in the second search space #1 shown in FIG. 10as the resource information addressed to itself. Thereafter, the radioprocessing section 208 performs the reception process in the resourceblock #1 indicated by the resource information #1.

As described above, according to the first embodiment of the invention,by mapping the resource information (assign, grant) for each MTCterminal 20 in the second search space in the PDSCH, the resourceinformation for a large number of MTC terminals 20 can be contained.Further, since a number of the CCEs in the PDCCH can be suppressed, thesearch space in which the MTC terminal 20 performs the blind decodingcan be reduced. As a result, load related to the blind decoding in theMTC terminal 20 can be reduced. Notably, although an example in whichthe resource information for the respective MTC terminals 20 are mappedin the second search space was described above, the first embodiment isnot limited to this example. For example, communication controllinginformation for each MTC terminal 20 such as transmission power andtransmission rate, and other various types of information for each MTCterminal 20 may be mapped in the second search space.

(Operation of First Embodiment)

Hereabove, the configuration of the MTC terminal 20 of the firstembodiment of the invention was described. Next, an operation of theradio communication system 1 of the first embodiment of the inventionwill be described.

FIG. 12 is a sequence diagram showing the operation of the radiocommunication system 1 of the first embodiment of the invention. Thebase station 10 firstly decides a second search space for one MTC group(S310). Then, the control signal generating section 120 of the basestation 10 describes information indicating the decided second searchspace in the CCE in the PDCCH in a state capable of being identified byMTC-GP_RNTI assigned to the MTC group (S320). More specifically, thecontrol signal generating section 120 adds a check bit obtained by theCRC circuit 124 by masking the information indicating the second searchspace with the MTC-GP_RNTI to the CCEs.

Further, the data mapping section 128 of the base station 10 maps theresource information for each MTC terminal 20 belonging to the MTC groupin the second search space of the PDSCH in a state capable of beingidentified by C-RNTI assigned to each MTC terminal 20 (S330).Thereafter, the base station 10 transmits the PDCCH and the PDSCH(S340).

Then, when the MTC terminal 20 receives the PDCCH from the base station10, the blind decoding section 220 of the MTC terminal 20 performs theblind decoding on the respective CCEs in the PDCCH using the MTC-GP_RNTIassigned to itself (S350), and specifies the second search space for theMTC group including the terminal itself (S360).

Further, when the MTC terminal 20 receives the PDSCH from the basestation 10, the blind decoding section 220 of the MTC terminal 20performs the blind decoding on the second search space in the PDSCHusing the C-RNTI (S370), and acquires the resource information for theterminal itself (S380). Thereafter, the MTC terminal 20 performs thereception process or the transmission process in the resource blockindicated by the acquired resource information.

(Supplementation of First Embodiment)

As described above, the base station 10 of the first embodiment of theinvention transmits the PDCCH by describing the information indicatingthe second search space in the CCEs in the state capable of beingidentified by the MTC-GP_RNTI. However, a case in which the base station10 transmits the PDCCH by describing the resource information for theMTC terminal 20 in the CCEs in a state capable of being identified bythe C-RNTI of the MTC terminal 20 may also be possible.

Thus, the MTC terminal 20 may perform the blind decoding of the PDCCH byusing both the MTC-GP_RNTI and the C-RNTI. Even in the case ofperforming the blind decoding of the PDCCH by using both the MTC-GP_RNTIand the C-RNTI, since the search space is made small according to thefirst embodiment of the invention, load on the MTC terminal 20 can besuppressed sufficiently.

Alternatively, in a case where it is determined that the base station 10cannot handle the MTC-GP_RNTI, the MTC terminal 20 may perform the blinddecoding by using only the C-RNTI. Notably, as the case in which thebase station 10 cannot handle the MTC-GP_RNTI, a case in which the MTCterminal 20 is connected to a new base station 10 by a hand-over, or acase in which the base station 10 does not have a capability to handlethe MTC-GP_RNTI is expected.

Alternatively, as will be described with reference to FIG. 13, the MTCterminal 20 may change the RNTI to be used in the blind decoding byrequesting a setting change to the base station 10.

FIG. 13 is a sequence diagram showing an example of a method of changingthe RNTI used for the blind decoding. As shown in FIG. 13, in the casewhere the MTC terminal 20 performs the blind decoding of the PDCCH byusing both the MTC-GP_RNTI and the C-RNTI, a setting request ofMTC-GP_Only_Mod can be transmitted to the base station 10 (S410).

When the setting request is received, the base station 10 sets theMTC-GP_Only_Mod that describes the information indicating at least thesecond search space for the MTC group to which the MTC terminal 20belongs in the CCE in a state capable of being identified by theMTC-GP_RNTI. Then, the base station 10 transmits a setting confirmingsignal of the MTC-GP_Only_Mod to the MTC terminal 20 (S420). Notably,the base station 10 may transmit the setting confirming signal of theMTC-GP_Only_Mod to all of the MTC terminals belonging to the MTC group.

After receiving the setting confirming signal of the MTC-GP_Only_Mod,the MTC terminal 20 performs the blind decoding by using only theMTC-GP_RNTI.

Thereafter, when the MTC terminal 20 transmits a release request of theMTC-GP_Only_Mod to the base station 10, (S430), the base station 10releases the setting of the MTC-GP_Only_Mod, and transmits a releaseconfirming signal of the MTC-GP_Only_Mod to the MTC terminal 20 (S440).After having received the release confirming signal of theMTC-GP_Only_Mod, the MTC terminal 20 again performs the blind decodingof the PDCCH using both the MTC-GP_RNTI and the C-RNTI.

2-2. Second Embodiment

Hereabove, the first embodiment of the invention was described. Now, asecond embodiment of the invention will be described. Notably, since thesecond embodiment to the seventh embodiment described below have a largenumber of portions in common with the first embodiment, detaileddescriptions for the portions in common with the first embodiment willbe omitted. Further, the second embodiment to the seventh embodimentwill be described by reusing the configurational diagram of the basestation 10 shown in FIG. 9 and the configurational diagram of the MTCterminal 20 shown in FIG. 11.

FIG. 14 is an explanatory diagram showing an example of disposition ofthe second search space for a certain MTC group. As shown in FIG. 14, abase station 10 may dispose second search spaces #1 to #3 at a sameposition that one CCE #1 indicates over a plurality of sub frames.

In this case, an MTC terminal 20 needs to know over how many sub framesthe second search spaces are to be disposed at the same position. Due tothis, the base station 10 may notify a number of the sub frames in CCE,or may notify the number of the sub frames to the MTC terminal 20 inadvance.

According to this second embodiment, since the number of the CCEs inPDCCH can further be reduced, load related to blind decoding on the MTCterminal 20 can further be reduced.

2-3. Third Embodiment

As described with reference to FIG. 7, typically, after searching CCE inPDCCH in a frequency direction, an MTC terminal 20 searches thefollowing Ofdm symbol again in the frequency direction. Due to this, inan LTE, a search in the frequency direction with a minimum width of 5MHz and a maximum width of 20 MHz is required.

However, from viewpoints that the MTC terminal 20 in some cases isrequired to have an extra low power consumption, and of an operationefficiency of a digital circuit, it is effective to make the searchwidth in the frequency direction be 5 MHz or less, for example, 1 MHz orless.

Thus, the base station 10 of the third embodiment disposes the CCEs forthe same MTC group in a predetermined sub carrier. Hereinbelow, specificdescriptions will be given with reference to FIG. 15.

FIG. 15 is an explanatory diagram showing an example of disposition ofthe CCEs for each MTC group. As shown in FIG. 15, the base station 10 ofthe third embodiment for example disposes CCE for an MTC terminal 20belonging to an MTC group 1 in a sub carrier x, and disposes CCE for anMTC terminal 20 belonging to an MTC group 2 in a sub carrier y. Notably,the base station 10 may notify the MTC terminals 20 in advance ofinformation indicating which sub carrier the CCE for each MTC group isgoing to be disposed in.

According to the above configuration, the MTC terminal 20 belonging tothe MTC group 1 can simply perform the blind decoding only on the subcarrier x in a time direction, and the MTC terminal 20 belonging to theMTC group 2 can simply perform the blind decoding only on the subcarrier y in the time direction. Thus, according to the thirdembodiment, load related to the blind decoding in the MTC terminal 20can significantly be reduced.

2-4. Fourth Embodiment

In the above embodiment, an example in which the MTC terminals 20 belongto one MTC group and one MTC-GP_RNTI is assigned was described. On theother hand, a case in which the MTC terminals 20 are grouped separatelyfor uplink and downlink is also expected. The fourth embodiment focuseson this feature, and MTC terminals 20 of the fourth embodiment belong toa plurality of MTC groups, and a plurality of MTC-GP_RNTIs are assigned.Hereinbelow, a specific example will be described with reference to FIG.16.

FIG. 16 is an explanatory diagram showing a specific example of an MTCgroup to which MTC terminals 20 belong. As shown in FIG. 16, the MTCterminals 20 of the fourth embodiment belong to an uplink MTC group anda downlink MTC group. For example, an MTC terminal 20A belongs to adownlink MTC group 1 and an uplink MTC group 1, and an MTC terminal 20Bbelongs to the downlink MTC group 1 and an uplink MTC group 3.

Due to this, MTC-DownLink_RNTI that is a downlink group identifier andMTC-UpLink_RNTI that is an uplink group identifier are assigned to eachMTC terminal 20.

In this case, a base station 10 generates the CCE including informationindicating a second search space for the uplink by using theMTC-UpLink_RNTI, and generates the CCE including information indicatinga second search space for the downlink by using the MTC-DownLink_RNTI.

For example, in a case of describing the information indicating thesecond search space for the uplink MTC group 1 in the CCE #4 shown inFIG. 17, the base station 10 generates the CCE #4 by using theMTC-UpLink_RNTI assigned to the uplink MTC group 1. Similarly, in a caseof describing the information indicating the second search space for thedownlink MTC group 2 in the CCE #5 shown in FIG. 17, the base station 10generates the CCE #5 by using the MTC-DownLink_RNTI assigned to thedownlink MTC group 2.

Due to this, the MTC terminal 20 can extract the CCE for the MTC groupto which the MTC terminal 20 belongs by performing blind decoding oneach CCE in the PDCCH by using the MTC-DownLink_RNTI and theMTC-UpLink_RNTI.

2-5. Fifth Embodiment

As described above, the first embodiment to the fourth embodiment makethe search space in the PDCCH small by using the second search space.With respect to this, the fifth embodiment to the seventh embodimentdescribed below make the search space in the PDCCH small by describingthe resource information shared by a plurality of MTC terminals 20configuring an MTC group in the CCE. Hereinbelow, the fifth embodimentto the seventh embodiment will orderly be described.

(Sharing Downlink Resource Information)

As applications of an MTC terminal 20, applications for reportingaccumulated information such as reporting sales performance of a vendingmachine, reporting used amount of gas or water are primarily expected.In such cases, a base station 10 can use a common command forinstructing a plurality of MTC terminals 20 to report the accumulatedinformation.

Thus, the base station 10 describes resource information indicating aresource block to which the plurality of MTC terminals 20 in an MTCgroup is to perform a reception process in the CCE. Further, the basestation 10 transmits the CCE in a state capable of being identified byMTC-GP_RNTI by adding a check bit based on the MTC-GP_RNTI assigned tothe MTC group to the CCEs.

Then, the plurality of MTC terminals 20 in the MTC group performs blinddecoding using the MTC-GP_RNTI, and extracts the CCE identified by theMTC-GP_RNTI. Further, the plurality of MTC terminals 20 in the MTC groupsimultaneously performs the reception process in the resource blockindicated by the resource information described in the extracted CCE.

According to the above configuration, since the resource information tothe respective MTC terminals 20 does not need to be described indifferent CCEs, the search space in the PDCCH can further be madesmaller.

(Sharing Uplink Resource Information)

In an uplink, if the plurality of MTC terminals 20 performs atransmission process in the same resource block, uplink data collapsesat the base station 10. Thus, the base station 10 describes resourceinformation indicating a reference resource block for the uplink of theMTC group in the CCE. Further, the base station 10 transmits the CCE ina state capable of being identified by MTC-GP_RNTI by adding a check bitbased on the MTC-GP_RNTI assigned to the MTC group to the CCEs.

Then, the plurality of MTC terminals 20 in the MTC group performs blinddecoding using the MTC-GP_RNTI, and extracts the CCE identified by theMTC-GP_RNTI. Further, the plurality of MTC terminals 20 in the MTC groupspecifies the reference resource block indicated by the resourceinformation described in the extracted CCE, and performs thetransmission process in the resource block that is in a positionalrelationship with the reference resource block as set in advance.Hereinbelow, this feature will be described more specifically withreference to FIG. 18.

FIG. 18 is an explanatory diagram showing a relationship of a referenceresource block and an uplink resource block of each MTC terminal 20. Asshown in FIG. 18, for example, resource information indicating aresource block #1 as the reference resource block of the uplink of a MTCgroup 1 is described in CCE #6.

Here, it is assumed that the MTC group 1 is configured of MTC terminals20A to 20D, and a relative position of a resource block to be used forthe uplink by each MTC terminal 20 from the reference resource block isset. In this case, the MTC terminals 20A to 20D specify the resourceblock #1 that is the reference resource block, and perform thetransmission process by using the resource block that is at the setrelative position from the reference resource block.

For example, a case of a setting in which the reference resource blockis an origin, and resource blocks that are adjacent in a time directionare used in an order of the MTC terminals 20A, 20B, 20C, and 20D will beassumed. In this case, as shown in FIG. 18, the MTC terminal 20A usesthe resource block #1 that is the reference resource block, the MTCterminal 20B uses a resource block #2 that is adjacent with the resourceblock #1 in the time direction. Similarly, the MTC terminal 20C uses aresource block #3 that is adjacent with the resource block #2 in thetime direction, and the MTC terminal 20D uses a resource block #4 thatis adjacent with the resource block #3 in the time direction.

As a modification, settings may be made with a reference resource blockas an origin to use resource blocks that are adjacent in a frequencydirection in an order of MTC terminals 20A, 20B, 20C, and 20D. In thiscase, as shown in FIG. 19, the MTC terminal 20A uses a resource block #1that is the reference resource block, and the MTC terminal 20B uses theresource block #5 that is adjacent to the resource block #1 in thefrequency direction. Similarly, the MTC terminal 20C uses the resourceblock #6 that is adjacent to the resource block #5 in the frequencydirection, and the MTC terminal 20D uses the resource block #7 that isadjacent to the resource block #6 in the frequency direction.

Notably, the base station 10 may signal the positional relationship ofthe resource block to which each MTC terminal 20 is to perform thetransmission process and the reference resource block in advance to eachMTC terminal 20. Further, although an example in which the fifthembodiment is implemented by the MTC-GP_RNTI was described, the fifthembodiment may be implemented by replacing the MTC-GP_RNTI with theC-RNTI. For example, in a case of not being able to handle theMTC-GP_RNTI, the base station 10 can allot the same C-RNTI to aplurality of MTC terminals 20, and the C-RNTI may be used in a similarway as with the above MTC-GP_RNTI.

(Operation of Fifth Embodiment)

Hereabove, sharing of the resource information in the fifth embodimentwas described. Now, an operation of the radio communication system 1according to the fifth embodiment will be described with reference toFIG. 20.

FIG. 20 is an explanatory diagram showing the operation of the radiocommunication system 1 of the fifth embodiment. As shown in FIG. 20, thebase station 10 transmits relative position information indicating thepositional relationship of the resource blocks to which the MTCterminals 20 are to perform the transmission to the MTC terminals 20 inadvance (S510).

Thereafter, the control signal generating section 120 of the basestation 10 describes the resource information for each MTC terminal 20belonging to the MTC group in a state capable of being identified by theMTC-GP_RNTI assigned to the MTC group to the CCEs in the PDCCH (S520).Specifically, the control signal generating section 120 adds the checkbit obtained by the CRC circuit 124 by masking the resource informationfor each MTC terminal 20 with the MTC-GP_RNTI to the CCEs. Then, thebase station 10 transmits the PDCCH including the CCE in which theresource information for each MTC terminal 20 is described (S530).

Then, when each MTC terminal 20 receives the PDCCH from the base station10, the blind decoding section 220 of the MTC terminal 20 performs blinddecoding on each CCE in the PDCCH by using the MTC-GP_RNTI assigned toitself (S540), and obtains the resource information for the MTC groupincluding itself (S550).

Here, in a case where the obtained resource information indicates adownlink resource block (S560), the MTC terminal 20 performs thereception process in the resource block indicated by the resourceinformation (S 570).

On the other hand, in a case where the obtained resource informationindicates an uplink resource block (S560), the MTC terminal 20 performsthe transmission process in the resource block that is in the positionalrelationship as indicated by the relative position information with thereference resource block indicated by the resource information (S 580).

As described above, according to the fifth embodiment, due to no longerbeing necessary to describe the resource information for each MTCterminal 20 to the respective CCEs, the search space in the PDCCH can bemade small. As a result, load related to the blind decoding in the MTCterminals 20 can be reduced.

2-6. Sixth Embodiment

The sixth embodiment is implemented by adapting the third embodimentdescribed with reference to FIG. 15 to the fifth embodiment.Specifically, a base station 10 according to the sixth embodimentdisposes a CCE including resource information for one MTC group in apredetermined sub carrier. According to the configuration, since an MTCterminal 20 simply needs to perform blind decoding on only thepredetermined sub carrier in a time direction, load related to the blinddecoding in the MTC terminal 20 can be reduced significantly.

2-7. Seventh Embodiment

The seventh embodiment is implemented by adapting the fourth embodimentdescribed with reference to FIG. 16 to the fifth embodiment.Specifically, an MTC terminal 20 of the seventh embodiment belongs to anuplink MTC group and a downlink MTC group. Due to this, the MTC terminal20 is assigned with MTC-DownLink_RNTI that is a group identifier fordownlink, and MTC-UpLink_RNTI that is a group identifier for uplink.

In this case, the base station 10 generates the CCE including the uplinkresource information of the MTC group by using the MTC-UpLink_RNTI, andgenerates the CCE including the downlink resource information by usingthe MTC-DownLink_RNTI.

Due to this, the MTC terminal 20 can extract the CCE for the MTC groupto which the MTC terminal 20 belongs by performing blind decoding oneach CCE in the PDCCH by using the MTC-DownLink_RNTI and theMTC-UpLink_RNTI.

3. CONCLUSION

As described above, according to the first embodiment to the fourthembodiment of the invention, the resource information for a large numberof MTC terminals 20 can be stored by mapping the resource information(assign, grant) for each MTC terminal 20 in the second search space inthe PDSCH. Further, since a number of the CCEs in the PDCCH can besuppressed, the search space in which the MTC terminal 20 performs theblind decoding can be reduced. As a result, load related to the blinddecoding in the MTC terminal 20 can be reduced.

Further, according to the fifth embodiment to the seventh embodiment ofthe invention, the resource information described in the CCE in thePDCCH can be shared by the plurality of MTC terminals 20 in the MTCgroup. Due to this, the resource information for each MTC terminal 20 nolonger needs to be described in separate CCEs, so the search space inthe PDCCH can be made small. As a result, load related to the blinddecoding in the MTC terminals 20 can be reduced.

Notably, although preferred embodiments of the invention have beendescribed in detail with reference to the attached drawings, theinvention is not limited to these examples. A person skilled in the artfind various alterations and modifications within the scope of theappended claims, and it should be understood that they will naturallycome under the technical scope of the present invention.

For example, respective steps in the processes by the base station 10and the MTC terminal 20 in the description do not necessarily beperformed in chronological orders as described in sequence diagrams. Forexample, the respective steps in the processes by the base station 10and the MTC terminal 20 may be performed in orders different from theorders described the in sequence diagrams, or may be performed inparallel.

Further, computer programs for causing hardware such as CPUs, ROMs, andRAMs installed in the base station 10 and the MTC terminal 20 to exhibitsimilar functions as the respective configurations of the base station10 and the MTC terminal 20 may be produced. Further, storage mediastoring such computer programs may also be provided.

REFERENCE SIGNS LIST

-   10 Base station-   12 MME-   14 S-GW-   16 PDN-GW-   20 MTC terminal-   30 MTC server-   104,204 Antenna-   108, 208 Radio processing section-   112, 212 Storage section-   116 Scheduler-   120 Control signal generating section-   124, 224 CRC circuit-   128 Data mapping section-   220 Blind decoding section

1. A base station, comprising: a central processing unit (CPU) configured to: generate a control signal which includes: reference information for a plurality of radio terminals, and information indicating a number of a plurality of sub frames over which a reference region is in a frame, wherein the reference information indicates a position of the reference region in a data region of the frame; and generate a data signal based on resource information for the plurality of radio terminals in the reference region.
 2. The base station according to claim 1, wherein the control signal is in a control region of the frame.
 3. The base station according to claim 1, wherein the control signal is a Phy Downlink Control Channel (PDCCH), and the PDCCH includes a plurality of Control Channel Elements (CCEs).
 4. The base station according to claim 1, wherein the CPU is further configured to transmit a radio signal in the frame to the plurality of radio terminals.
 5. The base station according to claim 1, wherein the CPU is further configured to allocate the resource information for the plurality of radio terminals over the plurality of sub frames.
 6. The base station according to claim 1, wherein the control signal further includes the resource information in a resource block of the frame.
 7. The base station according to claim 6, wherein the control signal is provided by an upper layer of the resource block.
 8. The base station according to claim 1, wherein the control signal is controlled based on a dedicated signaling operation.
 9. The base station according to claim 1, wherein the reference information for each of the plurality of radio terminals is identified based on a terminal identifier of each of the plurality of radio terminals.
 10. The base station according to claim 1, wherein the resource information is one of uplink resource information or downlink resource information.
 11. The base station according to claim 1, the CPU is further configured to notify the reference information by the control signal.
 12. A method, comprising: in a base station: generating a control signal in a control region of a frame, wherein the control signal includes: reference information assigned to each of a plurality of radio terminals, and information indicating a number of a plurality of sub frames over which a reference region is in the frame, wherein the reference information indicates a position of the reference region in a data region of the frame; and generating a data signal based on resource information for each of the plurality of radio terminals in the reference region.
 13. A non-transitory computer-readable medium having stored thereon, computer-executable instructions, which when executed by a computer, cause the computer to execute operations, the operations comprising: generating a control signal in a control region of a frame, wherein the control signal includes: reference information assigned to each of a plurality of radio terminals, and information indicating a number of a plurality of sub frames over which a reference region is in the frame, wherein the reference information indicates a position of the reference region in a data region of the frame; and generating a data signal based on resource information for each of the plurality of radio terminals in the reference region.
 14. A radio communication system, comprising: a plurality of radio terminals; and a base station configured to: generate a control signal which includes: reference information for the plurality of radio terminals, and information indicating a number of a plurality of sub frames over which a reference region is disposed in a frame, wherein the reference information indicates a position of the reference region in a data region of the frame; and generate a data signal based on resource information for the plurality of radio terminals in the reference region.
 15. A radio terminal, comprising: a central processing unit (CPU) configured to: receive a radio signal, wherein the radio signal is transmitted in a frame from a base station, and the frame includes a control region and a data region; acquire reference information for the radio terminal from a control signal in the control region, wherein the control signal includes information indicating a number of a plurality of sub frames over which a reference region is in the frame, and the reference information indicates a position of the reference region in the data region; and acquire a data portion for the radio terminal from a data signal in the reference region within the data region.
 16. The radio terminal according to claim 15, wherein the CPU is further configured to acquire the data portion from the data signal received in the reference region within the data region over the plurality of sub frames.
 17. The radio terminal according to claim 16, wherein the CPU is further configured to acquire the plurality of sub frames over which the reference region is consecutively arranged.
 18. The radio terminal according to claim 15, wherein the control signal is a Phy Downlink Control Channel (PDCCH), and the PDCCH includes a plurality of Control Channel Elements (CCEs).
 19. The radio terminal according to claim 15, wherein the reference information for the radio terminal is identified based on a terminal identifier of the radio terminal.
 20. A method, comprising: in a radio terminal: receiving a radio signal, wherein the radio signal is transmitted in a frame from a base station, and the frame includes a control region and a data region; acquiring reference information for the radio terminal from a control signal in the control region, wherein the control signal includes information indicating a number of a plurality of sub frames over which a reference region is in the frame, and the reference information indicates a position of the reference region in the data region; and acquiring a data portion for the radio terminal from a data signal in the reference region in the data region. 